Troubled apparel giant Gap Inc finally had some good news on Thursday when it posted an 11 per cent jump in October same-store sales after 29 consecutive monthly falls and lifted its third quarter earnings outlook.

The San Francisco-based operator of nearly 4,300 stores said total sales for last month soared 17 per cent to $1.2 billion from $1bn in the year-ago period, with quarterly sales up nine per cent to $3.6bn from $3.3bn in 2001.

It said Gap domestic and Gap international October same-store sales rose one per cent and five per cent, respectively, with Banana Republic same-store sales up six per cent and Old Navy up 24 per cent.

"Overall, October results across all brands significantly exceeded our beginning of month expectations," said CFO Heidi Kunz in a statement.

"We saw a substantial increase in average unit retail, driven by greater regular price selling and higher markdown margins. Traffic was negative, but we did see improvement from prior months."

Gap said it now expects third quarter earnings per share in the range of 12 to 14 cents, due to significant margin improvement in October.

It added moves to clear the inventory backlog caused by the West Coast port closure have progressed more quickly than expected, but it still anticipates delays of up to a month in some holiday deliveries to stores.

"While it is difficult to assess the earnings risk related to the port closure, we anticipate the impact to fourth quarter will be in the middle of two to seven cents per share range previously given," Ms Kunz added.